1. Field of the Invention
This invention relates to a process for producing a multiplicity of microfluidic arrangements, particularly nozzle arrangements, from a plate-shaped composite structure comprising groove structures with dimensions in the micrometer range and to an atomiser comprising a nozzle arrangement of this type.
2. Description of Related Art
A process of the type to which the present invention is directed is known from U.S. Pat. No. 5,547,094.
Nozzle arrangements of the type in question are employed for atomising liquid into very fine droplets by pressing the liquids under a high pressure through a nozzle opening of small cross-section. Amongst their other applications, nozzle arrangements of this type are employed in the medical field for aerosols for inhalation purposes, for example. Stringent demands with regard to droplet size are made on a nozzle arrangement of the type in question, since for inhalation applications, for example, a sufficiently large proportion of the droplets should have a diameter less than 6 μm in order to enter the lungs satisfactorily. In general, particles or droplets with a diameter less than 10 μm are considered as being respirateble.
U.S. Pat. No. 5,547,094 relates exclusively to block-like nozzle arrangements for applications of this type, and to methods of producing large numbers of block-like nozzle arrangements such as these of consistently high quality. With this known process, it is also possible to incorporate a filter, or even multi-stage filters, in the nozzle arrangement.
The overall content of the disclosure of U.S. Pat. No. 5,547,094 is made part of the disclosure of the present patent application by reference thereto. All the process steps of a corresponding production process which are disclosed there, and all the material specifications which are disclosed there, as well as the tools which are used, etc., can also be used within the scope of the process according to the present invention. Further disclosure regarding these nozzle arrangements can be found in International Patent Application Publications WO 94/07607 A1 and WO 99/16530 A1.
The known process firstly involves the production of a plate-shaped composite structure which comprises two plates with intrinsically planar surfaces which are fixedly and two-dimensionally joined to each other. Further plates can also optionally be added. It is essential that the nozzle arrangements in the plate-shaped composite structure are created by providing a multiplicity of recurring groove structures, each of which corresponds to a nozzle arrangement, in an intrinsically planar surface of one of the plates which is joined to the intrinsically planar surface of the other plate. The groove structures can optionally also be disposed in both the mutually facing surfaces of the two plates which are relevant here and which are joined to each other. In the prior art, a particularly preferred combination is a composite of a silicon plate and a glass plate, wherein other variants are also mentioned.
The groove structures ultimately form the flow channels of the nozzle arrangements, which preferably have dimensions in the micrometer range. To give an idea of the order of magnitude of the groove structures, the prior art mentions structure heights between 2 and 40 μm, preferably between 5 and 7 μm, and cross-sectional areas of the nozzles between about 25 and about 500 μm2.
Separate nozzle arrangements are obtained from the plate-shaped composite structure comprising a multiplicity of nozzle arrangements by separating the plate-like composite structure, by mechanical machining, along parting lines which extend between two groove structures. Nozzle arrangements of small surface area, which were formerly block-like, then exist separately. According to the prior art, separation by mechanical machining is effected in particular by sawing with a circular saw, preferably with a diamond circular saw which is operated at high speed. Nicking and breaking of larger plate-shaped composite structures are also cited as an alternative, for example. Both these machining steps can also be combined with each other, namely sawing can be carried out in first step, followed by completion in a second step by breaking or by separation by laser beam.
With regard to the production of the composite structure, reference is made in particular to field-assisted bonding, and also to other joining techniques including adhesive bonding, ultrasonic bonding, etc.
With this process, which is thus assumed to be known, for the production of nozzle arrangements from a plate-shaped composite structure comprising groove structures which have dimensions in the micrometer range, the problem arises that the groove structures are contaminated during mechanical machining, particularly by sawing. A liquid cooling lubricant, particularly one based on water, is normally used during mechanical machining. Due to this, and due to the swarf entrained therein, under some circumstances, the groove structures become blocked so that, in practice, they can no longer be cleaned. The consequence is a high reject rate. In this respect, it should be taken into consideration that several hundred individual nozzle arrangements are firstly formed on a plate-shaped composite structure and these are then separated by a grid-like network of parting lines. The individual production of nozzle arrangements of this type is therefore completely inconceivable.
The problem disclosed above is not only applicable to the production of a multiplicity of block-like, separate nozzle arrangements from a plate-shaped composite structure to which the aforementioned prior art relates, but is also applicable to the manufacture of a multiplicity of microfluidic arrangements comprising corresponding groove structures from a plate-shaped composite structure in general. Apart from nozzle arrangements, this problem arises for other microfluidic arrangements which have no direct nozzle function, for example, filter arrangements or distribution arrangements.
For microfluidic arrangements in general, the plate-shaped composite structure is preferably mechanically machined along lines which extend between the groove structures and which are not necessarily parting lines, so that thereafter the microfluidic arrangements in the composite structure are individually separated or are separated into groups but are not completely separated, or are in fact individually separated but are completely separated into groups.